Windbox for furnace



Feb. 21, 1967 FlSHER 3,304,982

WINDBOX FOR FURNACE Filed July 9, 1964 4 Sheets-Sheet 1 Q INVENTOR. F I2 fioizard (ELI/M682 ATTORN EYS Feb. 21, 1967 FISHER WINDBOX FOR FURNACE4 Sheets-Sheet 2 Filed July 9, 1964 INVENTOR jeamrd J7. [Zii'er F I G. 4%@m ATTORNEYS Feb. 21, 1967 L. A. FISHER WINDBOX FOR FURNACE 4Sheets-Sheet 3 zZZ mice o Filed July 9, 1964 ATTORNEYS Feb. 21, 1967 L.A. FISHER 3,304,982

WINDBOX FOR FURNACE Filed July 9, 1964 4 Sheets-Sheet 4 INVENTOR.lkazmrd ./Z. 1 2% ATTO R N EYS United States 3,304,982 WINDBOX FORFURNACE Leonard A. Fisher, Blandford, Mass, assignor to The H. B. SmithCompany, Incorporated, Westfield, Mass., a corporation of MassachusettsFiled July 9, 1964, Ser. No. 381,457 Claims. (Cl. 158-15) This inventionpertains to air admission directors or registers for fuel burners, inparticular for forced draft burners-that embodiment of the inventionherein disclosed being equally useful in oil, gas-oil, or gas burners.Briefly stated, the device of the present invention comprises a fanwhich supplies air tangentially to a cylindrical or conical wind-boxwhich includes a perforated inner liner which defines the combustionzonethe liner being cooled by incoming air circulating between the linerand the outer wall of the shell or casing of the wind-box. To equalizethe air pressure about the periphery of the liner, and resultant inflowof air through the perforations in the liner, an air distributing scrollor spiral diaphragm is arranged between the liner and the outer wall ofthe windbox casing whereby the radial width of the passage thus defined,in which the air circulates, gradually diminishes from its entrance endto its discharge end, with provision for directing any air which doesnot pass inwardly through the perforations in the liner to move towardthe axis of the flame.

The principal object of the present invention is to provide meanswherein the perforated inner liner is so cooled by circulating air thatit may be made of lower cost materials than is usually thought necessaryin devices of this general type. This cooling of the liner makes itpossible to design apparatus of'this type with smaller dimensions thanusual because the walls of the liner may be made thinner than when madeof refractory materials, and as the liner is not exposed to so high atemperature as has been common heretofore, its useful life is increasedsince corrosion rates decrease rapidly as the temperature decreases.Such a relatively thin walled liner cools more rapidly than one made ofheavy refractory materials thus reducing damage to the atomizers (andassociated parts) during the off-cycles following firing periods and, onthe other hand, because of the low thermal capacity of the liner ascompared with liners made of heavy refractory materials, the burnercomes to equilibrium temperature more quickly than usual when startedinto operation.

Furthermore, the atomizers or gas ports are not exposed to so high aradiant temperature as usual, with a corresponding increase in usefullife, and since the cooler surface which surrounds the flame does notglow to the same degree as the usual refractory liner, a flame detectordevice, sensitive to the flame, is more positive in its action since itacts against a darker background.

Other objects and advantages of the invention will be pointed out in thefollowing more detailed description and by reference to the accompanyingdrawings wherein:

FIG. 1 is an elevation, showing the device of the present inventionmounted upon a truck to facilitate its assembly with and removal fromthe furnacethat side of the device being shown which faces the furnace;

FIG. 2 is a side elevation, omitting certain parts, of the device shownin FIG. 1;

FIG. 3 is a more-or-less diagrammatic rear elevation, to larger scalethan FIG. 1, partly in vertical section, omitting the truck, but showingthe shell of the wind-box and the fan casing, in accordance with onedesirable embodiment of the invention;

3,304,982 Patented Feb. 21 1967 free FIG. 4 is a side elevation, partlyin vertical section on the line 44 of FIG. 3;

FIG. 5 is a side elevation, to larger scale than FIG. 4, showing onedesirable form of inner liner for the windbox;

FIG. 6 is a vertical section substantially in the plane of the line 66of FIG. 4, but to larger scale;

FIG. 7 is a side elevation of the wind-box shown in FIG. 6, omitting theliner, with the upper portion in .vertical diametrical section;

FIG. 8 is a fragmentary vertical section, to larger scale, through theperforated inner liner showing the perforations therein anddiagrammatically indicating the path of air circulating about the linerand moving inwardly through the perforations; and 1 FIG. 9 is afragmentary vertical section illustrating the fan by means of which airis delivered to the wind-box.

Referring to FIGS. 1 and 2,.the numeral 10 designates the outer,generally cylindrical shell or casing of the windbox, this casing orshell being mounted upon a vertical plate 12 attached to or forming anintegral part of a wheeled truck 11, thus facilitating the assembly ofthe wind-box with the furnace or its removal from the latter, the truckalso supporting other parts, for example the burner motor and associatedelements. The housing 13 (FIGS. 1 and 3) for the fan, which provides theforced draft to the wind-box, is also supported by the truck.

As shown in FIGS. 4 and 7, the outer casing or shell 10 is provided witha flange 13a designed to receive bolts or to be welded to the plate 12for securing the shell to the plate. The shell (FIG. 3) has a tangentialhollow arm 14 projecting from its peripheral wall and defining theterminal portion of an inlet passage 15, and has a terminal flange 16(FIG. 3) to which there is connected, by bolts or otherwise, a flange 17at the end of the discharge arm 18 of the fan housing 13-this housinghaving a central inlet opening 20 (FIG. 3) and encasing a rotary fan 21(FIG. 9) mounted upon the shaft 22 of the fan motor 23-the latter havingan attaching flange 24 which receives bolts for securing it to the fancasing at the opposite side of the latter from the opening 20.Desirably, an inwardly converging air-directing collar 25 (FIG. 9) isarranged within the opening 20 and is secured to the casing 19 of thefan by bolts 26. Within the passage 15 (FIG. 3) in the hollow arm 14 ofthe casing 13, there is arranged an air-controlling damper 27 (FIGS. 3and 7) which'is fixed to a shaft 28 by means of which it may be adjustedthereby to constrict the passage more-or-less and thus vary the velocityand quantity of air which enters the casing 10.

Within the casing 10 and concentric therewith is an inner liner 30(FIGS. 4 and 5) which is here shown as cylindrical, and having thespaced, peripheral reinforcing ribs 31. While as here shown the liner iscylindrical, it is contemplated as within the scope of the invention tomake it tapering or frusto-conical. As shown in FIGS. 4 and 5, thisliner is provided with circumferentially extending rows of perforations32. These perforations may, for example, be inch in diameter and thecylinder or liner may, for example, be of 14 gauge, stainless steel,that is to say, approximately 0.074 inch in thickness. At its left-handend, as viewed in FIG. 5, the liner 30 hasa flange or angle brackets 33by means of which it is secured to the vertical supporting plate 12 asshown in FIG. 4.

The supporting plate 12 (FIG. 4) is provided with an opening 34 (FIG. 4)which is coaxial with the liner 30. A slightly convergent circularfrusto-conical part 35 is Q welded or otherwise secured at its largerend to the plate 12 in coaxial relation to the opening 34. The annularspace between the liner 30 and the part 35 is filled with refractorymaterial 36 in which is embedded the gas supply manifold 37 from whichproject the gas jet nipples 38this gas manifold being supplied by a pipe39, here shown as entering the shell at its lower part.

Within the part 35 and concentric therewith there is arranged afrusto-conical tube 39 of lesser diameter than the part 35, thusdefining the annular space 40 for the entry of primary air, if thelatter be used. The annular space Within the tube 39 is for thereception of a fuel atomizer F (FIG. 4) if oil is the fuel to be burned.The broken line C (FIG. 4) indicates the axis of the flame.

Within the discharge end portion of the casing 10, there is arranged atruncated, conical air-directing member 41 coaxial with the casing 10and whose larger end is fixed, as by welding, to the casing 10. Thismember 41 is operative to discharge air, which does not pass inwardlythrough the perforations 32 of the liner 30, in a convergent streamtoward the axis C of the burner flame. To prevent the air, thusdischarged, from taking a spiral course, a series of radial vanes 42(FIG. 3) is arranged within the cone 41.

In the annular space between the outer shell or casing 10 and the liner30, there is arranged a scroll or spiral diaphragm 43 (FIGS. 3, 6 and7), one end 43a of which (FIG. 6) is closely adjacent to the innersurface of the shell 10 at approximately the point of tangency of thewall 14a of the tubular branch 14 which connects the shell 10 and thefan casing-this scroll 43 progressively decreasing in diameter until itjoins the opposite wall 14b of the part 14 at 4311, where its end iscloser to the liner 30 than to the shell. The scroll, as here shown,encompasses the liner 30 through an arc of approximately 250. Thus, thespace S (FIGS. 3 and 6) between the scroll and the liner member 30gradually decreases from the point at which the air from the fan firstenters the space S, so that, although some of the air which enters thespace S passes inwardly through the perforations 32, a substantiallyconstant air pressure is maintained in space S. Thus approximately thesame quantity of air enters the liner 30 from all sides. As shown inFIG. 8, air, indicated by the arrows A flowing, under pressure,circumferentially about the perforated liner 30, enters the linerthrough the perforations 32 as shown by the arrows A and flows along theinner surface of the liner thus acting to keep the liner cool. Byautomatically modulating the damper blade 27 so as to reduce the size ofthe discharge passage from the fan, the velocity may be increased tokeep the liner 30 cool, while the volume decreases in proportion to thefuel rate. By so circulating cool air about and through the liner it ispossible to employ stainless steel, for example, as the liner, ratherthan the heavier and more expensive refractory materials commonlyemployed, thus making it possible to reduce the dimensions of the deviceas compared with those commonly in use.

While one desirable embodiment of the invention has herein beenillustrated and described by way of example, it is to be understood thatthe invention is broadly inclusive of any and all modifications whichfall within the terms of the appended claims.

I claim:

1. A burner device which comprises a wind-box having an outercylindrical casing and a liner of circular transverse section coaxialwith and Within the casing, the liner being of such diameter as toprovide an annular space between it and the casing, the liner definingthe space within which combustion takes place; characterized in that theliner is of sheet metal and of a thickness less than would be necessarywere it to be made of a nonmetallic, refractory material, the linerhaving a multitude of perforations therein spaced substantiallyuniformly about its entire periphery, means operative to deliver airinto said annular space in a tangential direction, and means so guidingsaid air that it moves peripherally about the liner in contact with theouter surface of the latter throughout its entire circumference and at apressure such that some of the air passes through the perforations andmoves circumferentially of the liner in contact with the inner peripheryof the latter, thereby keeping the liner at a temperature below thatwhich would cause deterioration of the sheet metal.

2. A burner device according to claim 1, having, in combination with theliner, a nozzle element for delivering fuel in an axial direction intoone end of the liner, further characterized in that the liner is of amaterial having 'a thermal capacity which is lower than though it weremade of usual non-metallic, refractory materials so that the burnercomes into equilibrium temperature more quickly than usual when startedinto operation and cools more rapidly than were it made of refractorymaterial, thereby reducing damage to the fuel delivery element during anoff-cycle following a firing period.

3. The combination according to claim 2, further characterized in havingmeans operative to direct air which escapes from said annular space,without passing through the perforations in the liner, toward the axisof the burner flame, and means to prevent the air, so directed towardthe axis of the burner flame, from rotating about said axis.

4. The combination according to claim 2, wherein scroll-shaped diaphragmis arranged within said annular space, encompassing the liner through anarc of approximately 250, one end of the diaphragm being adjacent to thewall of the casing and the other end being adjacent to the outer surfaceof the liner thereby gradually decreasing the eflective radial width ofsaid annular space, and so creating a substantially uniform air pressurecircumferentially of the liner that air, passing through theperforations, enters the liner throughout substantially its entirecircumference.

5. The combination according to claim 2, wherein the liner is of sheetmetal of a thickness of the order of 0.074 inch, and wherein theperforations in the liner are of the order of /1 inch in diameter.

6. The combination according to claim 2, wherein, at the delivery end ofthe casing, a truncated conical ring is arranged within the annularspace between the casing and the liner with its larger end adjacent tothe wall of the casing and with its smaller end spaced from the linerthereby providing an annular discharge opening through which air fromthe annular space may move in a generally conical annular stream towardthe axis of the burner flame.

7. The combination according to claim 6, wherein the conical ring isprovided with a series of peripherally spaced, internal, radial vanesoperative to oppose circulatory motion of the air as it escapes from thesmaller end of the ring.

8. The combination according to claim 2, wherein both the outer casingand the inner liner are cylindrical, and each is provided at one endwith a radial attaching flange, said flanges lying in the same plane,and, in combination therewith, a wheeled truck comprising a rigidvertical plate, means securing said flanges to said plate, a motordrivenfan supported by the truck which is operative to deliver air into theannular space between the casing and liner, said vertical plate havingtherein an opening coaxial with the liner wherein there are arrangedcoaxial tubular members defining between them a passage for the entranceof primary air, and a nozzle within the inner of the two concentrictubular members for delivering atomized fuel into the combustionchamber.

9. In combination, in a burner of the class described, a hollow cylinderwhich defines the combustion chamber, said cylinder having a peripheralWall of sheet metal of a thickness less than would be necessary were thecylinder to be made of non-metallic, refractory material, the wallhaving external axially spaced, peripheral stiffening ribs and havingsubstantially uniformly spaced perforations in the intervals between theribs, means for delivering atomized fuel in an axial direction into oneend of the cylinder, and means operative so to direct a gaseous coolingmedium as to cause it to flow peripherally of the cylinder in contactwith its inner and outer surfaces, respectively, thereby to preventdestructive overheating of the cylinder.

10. The combination according to claim 9, wherein the cylinder whichdefines the combustion chamber is of stainless steel of the order of0.074 inch in thickness, said cylinder being lighter in Weight and oflesser external diameter than were the wall of the combustion chamber tobe made of non-metallic, refractory material.

References Cited by the Examiner UNITED STATES PATENTS 1,380,740 6/1921Reid 1581.5 1,519,846 12/1924 Klefiel 158-1.5 1,636,161 7/1927 Woolery15876 2,390,056 12/1945 Cleaver et a1. 1581.5 2,549,427 4/1951 Clarksonl58--7 2,901,032 8/1959' Brola 1581.5 X

FOREIGN PATENTS 1,052,616 3/1959 Germany.

183,874 8/ 1922 Great Britain.

FREDERICK L. MATTESON, 111., Primary Examiner.

ROBERT A. DUA, Examiner.

1. A BURNER DEVICE WHICH COMPRISES A WIND-BOX HAVING AN OUTERCYLINDRICAL CASING AND A LINER OF CIRCULAR TRANSVERSE SECTION COAXIALWITH AND WITHIN THE CASING, THE LINER BEING OF SUCH DIAMETER AS TOPROVIDE AN ANNULAR SPACE BETWEEN IT AND THE CASING, THE LINER DEFININGTHE SPACE WITHIN WHICH COMBUSTION TAKES PLACE; CHARACTERIZED IN THAT THELINER IS OF SHEET METAL AND OF A THICKNESS LESS THAN WOULD BE NECESSARYWERE IT TO BE MADE OF A NONMETALLIC, REFRACTORY MATERIAL, THE LINERHAVING A MULTITUDE OF PERFORATIONS THEREIN SPACED SUBSTANTIALLYUNIFORMLY ABOUT ITS ENTIRE PERIPHERY, MEANS OPERATIVE TO DELIVER AIRINTO SAID ANNULAR SPACE IN A TANGENTIAL DIRECTION, AND MEANS SO GUIDINGSAID AIR THAT IT MOVES PERIPHERALLY ABOUT THE LINER IN CONTACT WITH THEOUTER SURFACE OF THE LATTER THROUGHOUT ITS ENTIRE CIRCUMFERENCE AND AT APRESSURE SUCH THAT SOME OF THE AIR PASSES THROUGH THE PERFORATIONS ANDMOVES CIRCUMFERENTIALLY OF THE LINER IN CONTACT WITH